1. Field of the Invention
This invention relates to a web fed die cutting press having a reciprocable ram wherein the web is incrementally shifted to bring each area of the web to be die cut to a work station and mechanism is provided for bringing the web longitudinally thereof along what may be called the X axis into alignment with indicium on the web, for rotating the die unit about an axis defined as .theta., and for shifting the die unit laterally of the web along a Y axis to assure precise registration of the die unit with an area of the web to be die cut, before the ram is shifted to effect die cutting of the defined aea of the web.
2. Description of the Prior Art
The prior art has not provided efficient die cutting presses which are effective to align a die unit with a defined area of web to be die cut on an extremely precise basis without sacrifice in the speed of operation of the press, while at the same time affording essentially automatic operation.
Die cut presses have heretofore been provided which in effect constitute sheet fed units with alignment indicia being read by sensor mechanism forming a part of the press and wherein the work sheet is shifted as required to bring an image thereon into proper registration with the die assembly. As can be appreciated though, it is usually not feasible to shift a web located at the work station of the die cut press in order to bring an image on the web into alignment with the die cut unit without first severing the area of the web next to be die cut from the web itself. For various reasons, this is not a desirable mode of operation, especially where the die cut areas of the web are to be knocked out at a station spaced from and independent of the work station of the die cut press.
It is also known to provide positioning systems which sense the disposition of an article relative to a sensor which are functional to very accurately locate the work piece with respect to two coordinate axes. For example, in the Heinz U.S. Pat. No. 3,207,904, an electro-optical positioning system is disclosed which is capable of providing both translational and rotational positioning of an article. The system is especially useful for positioning semi-conductor wafers during production of transistors where bonding of conductive leads to the wafer must be carried out on an extremely accurate basis. However, the Heinz system is not practical for accurate positioning of images to be die cut forming a part of an elongated web, absent severing of the individual image sections from the web prior to die cut thereof.
Registration assemblies have also heretofore been provided for controlling the positioning of webs, but these mechanisms have not incorporated interrelated components for effecting registration on X, Y and .theta. axes. In U.S. Pat. No. 3,919,561, fiber optics and photocells are used to sense marks on a web in the form of a transverse bar and an angled bar, but the assembly cannot provide accurate positioning of a die unit as accomplished in the present invention because of lack of provision for rotation of the die unit about the .theta. axis while maintaining the image area of the web to be die cut in proper alignment with a die cut unit.
Another optical readout system is discloed for example in U.S. Pat. No. 4,059,841 which uses four photocells in a square pattern to read information recorded as marks along a track but here again the system is not operable to register images on a web to be die cut by a combination of web movement and die unit rotation and lateral shifting to obtain precise registration of the die unit with the web before die cutting thereof.
U.S. Pat. No. 3,758,784 discloses an optical detecting head where a line or edge sensor depends on the provision of fiber optics and four photocells are arranged in a line transverse to an article mark or edge being sensed to indicate the location of the article relative to the sensor. This is an example of accurate registration mark sensing but not exemplary of article and die registration combining shifting of a web, and shifting and rotation of the die.
An automatic positioning system is shown in U.S. Pat. No. 4,151,451 which functions to control X and Y axes movement of a work piece carrying table which are shifted by respective servo-motors. Indicia on the work piece are appropriately sensed and the signals resulting therefrom employed to control shifting of the table. Movement of the tool is possible but no rotation of a die unit or the like in coordination with longitudinal shifting of the work piece was contemplated by the inventor.
Fiber optic position sensing and recording mechanism is set out in U.S. Pat. No. 3,658,430 but the signals produced are not used to adjust the disposition of a work piece.
U.S. Pat. No. 3,385,245 embodies photocell position sensing to control longitudinal advancement of a web. Four photocells spaced around a sewing machine needle sense the edge of the cloth to provide digital control signals which are connected to stepping motors that move a table carrying the work piece. Adjustment of the table is possible along X and Y axes. No rotation of a tool about a .theta. axis is provided.
U.S. Pat. Nos. 2,002,374 and 4,085,928 illustrate the use of photocell sensing (and in the case of the '928 patent the provision of fiber optics) of markings on a moving work piece to actuate a machine tool as in the '374 patent or a folding mechanism as in the '928 patent.
U.S. Patents which illustrate the use of photocell sensing generally, and in some instances with associated fiber optics, for lateral guidance of traveling webs in response to the sensing of either the edge of a web or a line or marks therealong include: Nos. 2,078,669; 2,082,634; 2,777,069; 2,962,596; 3,859,517; 3,919,560; 4,110,627; and 4,146,797.
The use of guide or registration marks for the alignment of a mask with a work piece, such as in the manufacture of integrated circuits is disclosed in U.S. Pat. Nos. 3,497,705, 3,683,195 and 3,796,497.
U.S. Pat. No. 4,109,158 suggests the use of photocells for controlling positioning of a flexible printed circuit board carrying work piece. Alignment of the board with a mask is accomplished by photocell sensing of light through X-axis extended and Y-axis extended slots as contrasted with sensing of imprinted markings. There is no teaching of X, Y and .theta. axes alignment of a die unit with images on a web to be die cut.
Devices which incorporate X and Y axes positioning of relatively movable objects by mechanism which is dependent on photocell sensing of patterns, fiber optic light guides and similar mechanisms are found in U.S. Pat. Nos. 3,385,244; 3,535,527; 3,539,260; 3,761,177; 3,840,739; 3,868,555; and 3,966,329.
Other noteworthy U.S. Pat. includes No. 4,406,949 which suggests apparatus for scanning a work piece for reference points thereon using electronic circuits wherein a laser beam is directed downward onto a wafer containing an integrated circuit die provided with targets which are sensed by the beam to provide die orientation; Pat. No. 4,376,584 wherein a circuit pattern printing system includes alignment apparatus for adjusting a printing mask; Pat. No. 4,053,250 wherein a work table is adjusted by a pneumatic logic circuit; Pat. No. 4,315,201 disclosing apparatus for aligning a mask and wafer each having alignment marks wherein the amount of relative deviation between the alignment marks on the mask and wafer is sensed and a reading effected only after coincidence is photoelectrically detected; Pat. No. 4,354,404, wherein the carriage of a machine tool is movable relative to a work piece by position sensing means; and Pat. No. 4,356,223, wherein a cross-shaped semi-conductor chip registration mark is used for precise positioning of the chip relative to a tool.
U.S. Pat. No. 4,089,242 discloses a method and apparatus for forming gaskets and the like which is capable of operating at faster speeds than die cut presses theretofor available but the unit does not have X, Y and .theta. axes registration of a die unit with preprinted images or other predetermined areas of the web to be successively die cut.